Metal oxide nanoparticles and polycyclic aromatic hydrocarbons alter nanoplastic's stability and toxicity to zebrafish

Co-occurrence of nanoplastics (NPs) with metal oxide nanoparticles (nMOx) and polycyclic aromatic hydrocarbons (PAHs) have been widely reported. However, there is a scarcity of information on their interactions and combined toxic effects. In this study, we used two different sized NPs [55 nm (NP1) and 100 nm (NP2)] to understand the effect of nMOx (nCuO and nZnO) and PAHs [chrysene (Chr) and fluoranthene (Flu)] on NPs' stability and toxicity to zebrafish. Results revealed that increasing the concentration of nMOx, zeta-potential increased, and charge reversal was observed in NPs suspension while PAH produced no major changes. Aggregation kinetics performed with nMOx exhibited higher aggregation of NPs in presence of NaCl that alleviated critical coagulation concentration. NP1 stabilized the size of otherwise unstable nMOx suspension in the tap-water for a longer period, whereas, aggregation was observed with NP2. The in vivo comet assay results showed that NP1 was more genotoxic than NP2 owing to their lower size. Interestingly the DNA damage was highest in NPs+nMOx followed by nMOx and NPs. Unlike nMOx, Chr/Flu+NPs showed reduced DNA damage as compared to NPs or PAH alone. Alteration in catalase activity and lipid peroxidation value indicated oxidative stress in all exposure groups.

Automated summary

The co-occurrence of nanoplastics with metal oxide nanoparticles and polycyclic aromatic hydrocarbons has been widely studied, yet little is known about their interactions and combined toxic effects. This research found that increasing the concentration of metal oxide nanoparticles led to aggregation of nanoplastics, while polycyclic aromatic hydrocarbons had no major impact on nanoplastic stability. The size of the nanoplastics played a role in genotoxicity, with smaller nanoplastics showing higher levels of DNA damage.